Interlocked switch



March 10, 1942- N. LEMMON INTERLOCKED SWITCH Filed March 10, 1939 2 Sheets-Sheet l LOAD lNVENTOR @3971, M

March 10, 1942. LEMMON INTERLOCKED SWITCH Filed March 10, 1939 2 Sheets-Sheet 2 INVENTO Patented Mar. 10, 1942 INTERLOCKED SWITCH George N. Lemmon, Homewood, Ala... assignor to Southern States Equipment Corporation, -Birmingham, Ala.

Application March 10,1939, Serial No. 260,951

5 Claims.

One purpose of this invention is to provide a means whereby electric power from either one of two sources may be supplied to a substation, or other receiver of high voltage power, with a minimum of delay in case abnormal conditions have occurred. One purpose is to provide automatic means to transfer a load from one feeder circuit to another when power has failed on the first circuit; a further purpose is to provide means to transfer the load back to the first circuit when normal conditions have been reestablished. Another purpose is to provide automatic means for operating various items of electrical equipmen in the manner to be described.

A further purpose is to accomplish the desired results with a minimum of equipment and at a low expense.

These purposes are accomplished in one way by feeding power to the substation, or other load, by means of two switches, operated by a single motor mechanism, and inter-connected by a quick-throw device.

Referring to the drawings, Fig. 1 is a diagram of one type of electrical installation in which this invention is used; Fig. 2 is a side view in partial section of the inter-connected crank mechanism which is one part of the installation; and Fig. 3 is a plan view ofthe crank mechanism.

Two incoming lines I, 2 are connectible to the station 3 through switches 4, 5. which may be air-break, group-operated switches of suitable design.

Let it be assumed that it is preferred to have line I furnish power to the substation 3; then Fig. 1 shows all members in normal positions.

Between the two switches 4, 5 is the crank mechanism 6; and a motor-mechanism 1 operates both switches. Transformers 8, 9 step down the voltage in the feeder circuits I, 2 and supply power to operate the apparatus. Relays II], II control the various circuits.

The device 6 is bolted to a suitable support and it includes two cranks l2; I3 biased together by the spring l4 and both pivoted on the shaft IS. The dog It and the arm l8 are both secured to the shaft l1 and are biased by the spring 2| towards the position shown in Fig. 3; a stop I9 prevents over-travel. The arm is an extension of the crank I2, and when turned towards the shaft I1 the arm 20 strikes the arm switch 25, 26, 21, 28 operates in step with the crank 29. Fixed to the shaft and insulated therefrom is the double collar engageable with three contact strips 26, 21, 28. The strip 26 is in constant contact with the collar 25 while 21 and 28, alternately, are in contact with a projection on 25. This makes a double-throw switch which changes its circuit as the crank 29 changes its position.

The relay Ill consists of an induction-disc motor which is driven by power from transformer 8 and which has a pinion center geared to a toothed segment 32 to which are attached two mercury-tube switches as indicated. Stops 33. 34 limit the travel of segment 32 about its pivot support 36. When power is on the line the segment 32 is raised. The switch 3| is closed and the switch 30 is open. Electrical circuits are shown in Fig. 1. Since the coil circuit of the relay II is opened by the switch 30 the contacts of relay II are also open, and the contact 21 is de-energized.

Operation is as follows:

When power goes off line I, relay I0 is deenergized and the weight of the members 30, 3| and 32 rotates the induction disc counter-clockwise, so the mercury switches change their position but with a definite time-delay. Therefore a momentary interruption of power on I does not affect the equipment; but if power stays off,

I then switch 3| is opened and switch 30 is closed.

This last energizes relay II, provided power is on line 2, and so closes the contacts of II, energizing 21 and so operating the motor 22. The motor revolves the shaft 23 which rotates the arm 29 through degrees. This opens the switch 4 and also pushes the crank I2 to the other end of its travel. The crank I3 is also pushed around by the projection I2, so switch 5 is closed and the arm I3 is engaged by the dog I6, as shown in Fig. 5.

At the same time the cam 25 has changed its.

When power comes back on the line I, the relay I is energized, and the slow clockwise revolutions of the induction disc 35 raise the segment 32 and change the switches 30 and 3| back to their former positions. This de-energizes I I and opens its circuit; it also energizes the motor through the switch 3| and the contacts 28-26. Therefore the succeeding half-revolution of the shaft 23 brings the crank 29 back to its original position and so closes the switch 4. The crank I3 does not move at first for I3 is held by the dog I6, but as the crank I2 approaches the end of its travel the arm 20 strikes the arm I8 and so knocks the dog IIi away from the notch in I3. Then the spring I4 instantly swings the crank I3 up to the crank I2 again, thereby opening the switch 5. r

Since the switch 4 makes initial contact before the contacts of switch 5 are fully separated, the power service is transferred from line 2 back to line I without any interruption at all to service at substation 3. Since lines I and 2 are parts of the same system and are in synchronism, opening the switch 5 does not build up any objectionable voltage across the switch 5 as it is opened.

It is obvious that manual operation of the crank 29, or its equivalent would still achieve one of the desired results in that the circuit would be opened when a transfer of load is made from I to 2, but the circuit would not be opened when a transfer is made from 2 back to I.

One familiar with the art can make other modifications of this mechanism without departing from the purpose and spirit of the invention,

and the claims are not limited to the details as shown. Thus the spring I4 may be replaced by a spring connected directly to the switch 5, without altering the operation of the complete system. Also the device 6 may be used to interconnect two switches which both open or both close with a single operation of the control members, instead of one open and one close, as here shown.

I claim:

1. In combination, two separate line switches, together with a separate mechanical unit interconnecting the said switches, the said unit including a base supporting two swing arms each with a pivot connection at its swing end, a connecting member between each of the said pivot connections and one of the said switches, means to bias one of said swing arms and its respective switch towards a certain position, holding means to retain the said swing arm away from the position towards which it is biased, and releasing means operable by motion of the said other swing arm to release the said holding means.

2. In combination, two separate line switches. a separate mechanical unit interconnecting the two said switches, the said unit including a supporting base, two swing arms mounted thereon, a pivotally connected link between each swing arm and one of said switches, means to bias the first of said swing arms and its switch towards a certain position, together with engaging means operable by the said second swing arm to engage the said first swing arm and to operate the said first switch arm and its switch away from the position towards which they are biased.

3. In combination, two separate line switches,

together with a separate unitary interconnecting device, the said device including two swing arms each pivotally mounted and with a pivotal connection between its swing end and one of said switches, means to bias the first of said arms and its switch towards a certain position, means operable by the second said swing arm to move the first said swing arm away from the position towards which it is biased, holding means to retain the said first swing arm in that position, and release means operable by the opposite motion of the second said swing arm to release the said holding means.

4. As an article of manufacture a separate unitary interconnecting unit between two separate electric line switches, said unit comprising a supporting base, two swing arms pivotally mounted thereon, pivotal connecting means between the swing end of each of said arms and one of said switches, means biasing one of said swing arms towards the other, stop means to limit the travel of the biased arm relative to the other arm, holding means to retain the biased arm away from the position towards which it is biased, and releasing means operable by the reversed motion of the other arm to release the said holding means.

5. In combination, two separate line switches; a separate mechanical interconnecting device between the two switches, the said device including a supporting base, two swing arms mounted thereon and each pivotally connected with one of said switches, engaging means between the two arms to limit their relative travel towards each other and to cause the first arm to carry the second arm with it when operated towards a certain position, holding means to keep the said second arm in the said certain position, and releasing means operable by motion of the said first arm away from the said certain position to release the said holding means; together with means to bias the said second arm and its switch away from the said certain position.

GEORGE N. LEMMON. 

